1. Field of the Invention
The present invention relates to a cold trap and a method of regenerating a cold trap.
2. Description of the Related Art
A cold trap is an apparatus for removing a gas from the environment by freezing and capturing the gas on its surface. Normally, a cooling apparatus such as a system for supplying a cooling fluid or a cryogenic refrigerator is provided in association with the cold trap so that the surface of the cold trap is cooled to a cryogenic temperature.
For example, patent document No. 1 describes using a cold trap in combination with a dry pump such as a turbomolecular pump. A cold trap is provided in the interior of a vacuum chamber pumped primarily by the dry pump. Gases with a smaller molecular weight such as water vapor are frozen and collected on the cold trap. Other gases with a relatively large molecular weight are pumped by the turbomolecular pump. According to the document, a high degree of vacuum is obtained as a result. A regeneration operation for melting and discharging the water molecules thus frozen and collected is performed after performing a pumping operation for a predetermined period of time. A coolant heated by a heater heats the cold trap. This causes the frozen and collected water vapor to be liquefied and drained via a drain pipe provided immediately below the cold trap.    [patent document No. 1] JP 9-313920
However, if the liquefied water or ice drops onto the turbomolecular pump, the turbomolecular pump may be adversely affected. In the worst case, the turbomolecular pump may be damaged. In another aspect, time required for regeneration for a cold trap represents a downtime for a vacuum chamber. Therefore, regeneration time is preferably as short as possible.